1. Field of the Invention
The present invention relates to a centrifugal blasting apparatus for blast cleaning or shot peening treatment of a selected surface of an object to be treated by throwing, with centrifugal force, pulverized abrasive material such as steel particles onto the surface.
2. Description of Related Art
A conventional centrifugal blasting apparatus is designed to use the force of gravity to supply pulverized material to its blade wheel, as disclosed in Japanese Patent 51-14314(B1) (corresponding to U.S. Patent application Ser. No. 703,397 filed on Feb. 5, 1969 in the name of James W. Forgel) and U.S. Pat. No. 3,788,010.
Another conventional centrifugal blasting apparatus is designed to separate pulverized abrasive material from the stream of airborne pulverized abrasive material and supply the so separated abrasive material to the blade wheel as disclosed in U.S. Pat. No. 4,095,378. This type of centrifugal blasting apparatus requires an abrasive material collector and an air-tight abrasive material ejector, which is connected to the outlet of the abrasive material collector.
The former centrifugal blasting apparatus cannot work if it is put in such a position that pulverized abrasive material cannot fall on its blade wheel by the force of gravity. Thus, the positioning of the apparatus is limited.
The latter centrifugal blasting apparatus is required to operate under the conditions that the inner pressure of the abrasive material collector is substantially lower than the surrounding atmosphere (for instance, by 50 mm Hg), and that it is difficult to reduce the size of the air-tight abrasive material ejector.